[TheMidasTouch]

Hey all, tough question here which I've been working on, and I'd love some help cracking.

Chlorine dioxide reacts with sodium peroxide, Na2O2, forming compound K (Mr = 90.5) as the only solid product. Compound K contains only sodium, chlorine and oxygen, and when dissolved in water does not produce a precipitate with aqueous silver nitrate.

When a given mass of K was strongly heated for a considerable time, a disproportionation reaction occurred and there was no change in the mass of the solid. The resulting solid was dissolved in water and the solution formed then gave a precipitate with aqueous silver nitrate. This solution required the addition of 15.8cm3 of 0.150moldm–3 aqueous silver nitrate for complete precipitation of the Cl– ions.

After the precipitate had been removed, the remaining solution was treated with SO2 to reduce all the remaining chlorine-containing species to Cl– ions. A further addition of 31.6 cm3 of 0.150 mol dm–3 aqueous silver nitrate was required for complete precipitation of these Cl– ions.

Deduce the formula of K. Write equations to represent the formation of K and the disproportionation reaction. Explain your deductions.

6 marks, for what it's worth.

Pretty sure the formula of K is NaClO2, but that's not from calculation, which I assume is what it's after. The equations it mentions are what's giving me the most trouble though.

2ClO2 + Na2O2 ---> 2NaClO2 + O2, maybe? Then 2NaClO2 ---> NaCl + O2 upon thermal decomp.? That's not disproportionation though, nor would the mass remain the same.

Thanks in advance for any *delete me*

[Borek]

Ignore initial reactions for now. See what you can deduce about the compounds after disproportionation from the data given.

How much is 31.6/15.8?

[TheMidasTouch]

Yeeah I gathered that it's twice as much AgNO3, so I'm looking for a 1:2 ratio perhaps?

The disproportination reactions I can come up with are:

3NaClO2 ---> NaCl + 2NaClO3

or

2NaClO2 ---> NaCl + NaClO4

Is the ratio relevant here?

[Borek]

Is the ratio relevant here?

Yes. Just by knowing ratio you should be able to reject one of the reactions you listed.